添加剂对HMX重结晶晶体形貌的影响

通过模拟计算与试验相结合的方法,研究了添加剂乙酰胺、丙烯酰胺、乙胺水溶液对重结晶HMX晶体形貌控制的影响.结果表明,3种添加剂对HMX重结晶晶体形貌影响的大小顺序为:乙酰胺＞丙烯酰胺＞乙胺,乙酰胺使晶体偏离球形化,丙烯酰胺具有使晶体向着球形化发展的趋势,由于乙胺与HMX晶面的附着能较小,乙胺对HMX重结晶晶体形貌改变不...     

γ-丁内酯重结晶HMX的粒度分级工艺

为了制备多种粒度的HMX，探索了用γ-丁内酯为溶剂重结晶HMX的原理，研究了HMX的γ-丁内酯溶液在不同过饱和度等条件下的结晶状况，通过控制稀释剂水的加入量和速度，以及结晶过程的搅拌强度等工艺条件，分别制备出符合GJB2335-95标准的6种粒度类别的HMX产品。结果表明，该方法工艺简单易行，溶剂便于回收且可循环使用，低耗，无污染。     

硝酸-水重结晶HMX工艺研究

硝酸-水（溶剂非溶剂法）重结晶β-HMX,通过优化工艺条件,制备出高能低感的球形化HMX晶体颗粒。实验结果表明,撞击感度与重结晶工艺密切相关。温度为5℃、搅拌速度为100r／min、稀释速率为0.375mL／min、静置时间为0min的条件下,重结晶出的HMX颗粒孔隙率较小,球形化程度较高,撞击感度较低。     

降感HMX的制备及性能测试

为了改善奥克托今(HMX)结晶形态并降低感度,以二甲基亚砜为溶剂,以水为非溶剂,以糊精为晶体控制剂,对普通HMX采用溶剂/非溶剂重结晶法处理,制备降感HMX。使用电子偏光显微镜、液相色谱仪分析测试了HMX重结晶前、后的晶体形貌和质量,表明重结晶后HMX的晶体颗粒更加规整圆滑,近似球形,并且纯度达到99.15%。撞击感度实验表明,重结晶后HMX的撞击感度比普通HMX降低32%。     

湿法研磨制备改性HMX及其机械感度研究

通过湿法研磨制备出不同粒度的改性HMX晶体,采用折光匹配法对其形貌进行表征,并测试了改性HMX的机械感度。讨论了研磨速率对HMX粒径的影响,以及改性前后HMX的机械感度,分析了湿法研磨对HMX机械感度的影响机理。结果表明,研磨速率为0.524m/s时得到的HMX粒度最小,为43.1μm,改性后的HMX摩擦感度降低60%,撞击感度降低68%,且研磨晶体粒度越小,晶体特性落高数值越大。晶体粒度及内部缺陷对机械感度的影响机制主要是研磨后晶体粒度减小且晶体内部缺陷减少,受到外力作用时,晶体内部热点产生和传播的概率降低。     

RDX粒度分级工艺研究

通过正交试验，给出影响RDX丙酮重结晶粒度分级工艺的主要因素。对照4类产品粒度标准，确定了该产品粒度分级的工艺条件，讨论了溶剂种类、溶液过饱和状态及溶剂蒸发速度对结晶过程的影响，分析确定了1～8类RDX粒度分级的工艺条件，并进行了优化试验。结果表明，丙酮重结晶工艺能够满足不同粒度级别RDX的生产。     

钢模压制下高品质HMX晶体的损伤规律

为了揭示粒度分布与压制期内含能晶体损伤程度的关系,研究了3种不同粒径的高品质HMX炸药在压制后微结构和粒度分布的变化。结果表明,随着HMX晶体粒径的增大,晶体表面逐渐形成裂纹,其尖端和棱角发生破碎。当晶体尺寸达到222.5μm时会出现明显的穿晶断裂。采用两种粒度的HMX级配,可减少对晶体中的损伤。压缩刚度法所得HMX的黏结强度和光电子能谱所得PBX造型粉的包复度表明,随着颗粒粒径的增大,炸药的包覆效果和力学强度降低,导致压制PBX中更多晶体的破碎。     

超临界CO2法制备超细HMX颗粒

考察了预膨胀压力、HMX丙酮溶液初始浓度、取样停留时间及其他因素对制备HMX超细微粒粒度和晶体性质的影响.制备的超细HMX微粒平均粒径在350 nm以下,一部分微粒粒度小于100 nm.结果表明,预膨胀压力对HMX颗粒尺寸的影响较大,压力增加,HMX平均粒度变小,粒度分布变窄;HMX丙酮溶液初始浓度对HMX的粒度和粒度分布有很大影响,初始浓度越小平均粒径就变小,粒度分布变窄.停留时间及喷嘴尺寸对颗粒粒度、粒度分布及其形貌都有不同程度的影响.     

炸药的超临界重结晶细化技术

从理论上分析了影响超临界重结晶细化结果的主要因素，并在超临界CO2中对HMX进行了大量的细化实验研究，结果表明，压力是控制细化结果粒度和粒度分布的主要因素。     

非溶剂制备细化HMX及其性能表征

以二甲基亚砜为溶剂,用喷雾重结晶细化法制备了HMX,研究了非溶剂(水、乙醇、氯代烷烃)的种类、溶剂与非溶剂的体积比以及非溶剂的温度对HMX晶体形貌的影响并分析了其影响机理。采用扫描电子显微镜(SEM)、激光粒度分析仪、X射线衍射仪(XRD)、差示扫描热量法(DSC)对其进行了表征和热分析。测试了细化HMX和原料HMX的撞击感度。结果表明,HMX细化最佳工艺条件是以35℃乙醇为非溶剂,溶剂与非溶剂体积比为1∶40,此时可获得中值粒径为616nm、粒径分布均匀、趋于球形且表面光滑的亚微米HMX;亚微米HMX表观活化能比原料HMX降低了13.75kJ/mol,与原料HMX相比具有更好的热安定性,特性落高从34.05cm升至79.10cm,撞击感度显著降低。     

高速撞击流法制备超细HMX炸药

利用高速撞击流法在不同的工艺条件下制备了超细HMX颗粒，研究了分散剂和制备工艺条件对HMX粒径的影响。结果表明，利用高速撞击流法可制备出纳米级超细HMX炸药颗粒。     

超临界流体重结晶制备HMX微细颗粒和结晶速率的研究

Microparticle formation and crystallization rate of 1,3,5,7-tetranitro-l,3,5,7-tetraazacyclooctane (HMX) in acetone solution using supercritical carbon dioxide antisolvent (GAS) recrystallization were studied. Scanning electronic microscopy, X-ray diffraction and infrared radiation were used to examine particle size, crystallinity and chemical structure. The results show that β-HMX microparticle in different average size (2--9.5μm) and with narrow size distribution were obtained by controlling the expansibility, expansion speed, initial concentration and temperature during recrystallization of HMX. The formation of nuclei may be a main cause of consumption of solute when the solution is expanded rapidly enough and the equilibrium concentration is lower, in which almost monodisperse microparticle can be obtained.     

Combustion mechanism of nitro ester binders with nitramines

The combustion of binary compositions of nitramines (HMX, RDX, Bi-HMX, and CL-20) with two nitro ester binders, one of which is characterized by gas-phase combustion, and the other by the burning-rate controlling reaction in the condensed phase, was studied in the pressure range 2–15 MPa. It is shown that in compositions with the binder characterized by gas-phase combustion, HMX in concentrations up to 50% acts as an inert additive. Depending on the size and concentration of HMX particles, three types of combustion of the mixtures can be identified: combustion along the binder layers, combustion as a single system, and the model of combustion with a coolant. At higher nitramine concentrations, combustion control passes to nitramine, and the burning-rate controlling reaction occurs in the liquid phase of nitramine. For Bi-HMX and CL-20 nitramines, which are less stable and more fast burning than HMX and in a mixture with a binder characterized by gas-phase combustion, only two combustion models are observed: the model with fast burning additives or combustion as a single unit. In compositions of the nitramines RDX and HMX with a binder burning by the c-phase mechanism, the combustion model with fast burning additives is applicable only in a narrow range of conditions. The compositions mostly burn only as a single unit, and the addition of nitramine increases the burning rate of nitro ester by transferring heat from the overlying zone to the condensed phase.     

Effect of Drying Conditions on the Particle Size,Dispersion State,and Mechanical Sensitivities of Nano HMX

Nano HMX was prepared using a bi‐directional rotation mill and dried in different liquids, at various temperatures, and under different conditions. It was revealed that the samples were caked seriously and the particles tend to aggregate with obviously increased size when dried through ordinary drying in different liquids at 70 °C, which also occurred after vacuum drying. The degree of caking and aggregation was enhanced with increasing temperature. The particles were prevented to grow and the samples were fluffy when supercritical drying, particularly freeze drying, was used. The mechanical sensitivities of the samples marked with I‐HMX, O‐HMX, and F‐HMX, which had average sizes of 120.36 μm, 1.18 μm, and 0.16 μm, respectively, were carried out. Compared with I‐HMX, the friction, impact, and shock sensitivities of O‐HMX were slightly lower, and a significant sensitivity decrease for F‐HMX happened with specific values of 28 %, 42.8 %, and 56.4 %, respectively, which demonstrated significant safety improvement.     

Thermal Sensitivity of HMX Crystals and HMX‐Based Explosives Treated under Various Conditions

The Five‐Second Explosion Point (5‐SEP) tests and the SEM detections in this research showed that the HMX crystals and the HMX‐based explosives treated under different conditions can possess different thermal sensitivities. That is to say, higher impurity, smaller granularity, and worse integrity of HMX crystals can make them more thermally sensitive. The addition of metal or metal oxide particles, especially nanoparticles to HMX can also enhance its thermal sensitivity. Meanwhile, coating of HMX crystals with polymers to form perfect PBX and to keep them undamaged are helpful to decrease their thermal sensitivity. Furthermore, the thermal sensitivity of temperature‐aged HMX changes differently in terms of the integrity of its particles. Therefore, it can be concluded that conditions which increase the surface energy of HMX crystals or which make the HMX molecules more active to decompose at lower temperature will increase the thermal sensitivity of HMX. Additionally, the variation in the thermal sensitivity of HMX treated under different conditions is generally more temperate than that of its mechanical sensitivity.     

Influence of Particle Size and Mixing Technology on Combustion of HMX/Al Compositions

In this work, two widely used components of high‐energy condensed systems – HMX and aluminium – were studied. Morphology, thermal behaviour, chemical purity and combustion parameters of HMX as a monopropellant and Al/HMX as a binary system were investigated using particles of different sizes. It was shown that in spite of the differences in composition and particle size, combustion velocities are almost identical for micrometer‐sized HMX (m‐HMX) and ultrafine HMX (u‐HMX) monopropellants under pressure from 2 to 10 MPa. Replacement of the micrometer‐sized aluminium with ultrafine one in the system with m‐HMX leads to a burning rate increase by a factor of 2.5 and the combustion completeness raise by a factor of 4. Two mixing techniques to prepare binary Al/HMX compositions were applied: conventional and ‘wet’ technique with ultrasonic processing in liquid. Applying wet mixing results in a burning rate increase of 18% compared to the conventional mixing for systems with ultrafine metal. The influence of the component's particle size and the composition microstructure on the burning rate of energetic systems is discussed and analysed.     

Effect of Sandpaper and Grain Size on Non‐Shock Initiated Reactions in HMX

Three grades of HMX samples, coarse (A), coarse with a small amount of fines (B), and ultra‐fine (F), were tested for impact sensitivity by ERL drop hammer. The Type 12A test used sandpapers of three different compositions, 120‐, 180‐grit Si/C and 180‐grit garnet. Reaction was accounted for by operator observation and microphone. The results showed different sensitivity for each of the HMX types. The F‐HMX was the smallest in average particle size and was the least sensitive to impact. The A‐HMX was the next most stable and the B‐HMX was the most sensitive to impact. The spent samples from the drop hammer testing of B‐HMX and F‐HMX were further evaluated with optical imaging. Conditions were selected that were near the DH₅₀ values of the specific HMX. Previous literature has cited localized hot spot formation to be the probable cause of non‐shock initiated reactions leading to impact sensitivity. This study yielded a plethora of samples exhibiting hot spots for HMX materials, both without and with proximity to grit particles. Hot spots in the proximity of grit particles gave the most dramatic hot spots, but both types of hot spots were exhibited in samples considered reacted and non‐reacted. The F‐HMX, even though the most stable to impact sensitivity, exhibited the most and best resolved hot spots of all the samples and conditions. Foreign objects were also observed in some of the samples. Previous work has shown metal particles coming from wear of the anvils used in the drop hammer experiment can also form hot spots. However, none of the samples here with metal particles exhibited, in proximity, hot spot formation.     

Study of the Elaboration of HMX and HMX Composites by the Spray Flash Evaporation Process

The Spray Flash Evaporation (SFE) process invented and developed at the NS3E laboratory allows obtaining different nanosized explosives (TNT, RDX, CL‐20…). This process is based on the very fast evaporation of the solvent due to the drastic modification of pressure and temperature leading to the crystallization of the molecules present in solution into nanometric or submicrometric particles. Here, we show the possibility to prepare pure HMX (Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) or HMX based composites at the nanoscale using this process. This study mainly focuses on the size, morphology and crystallographic phases obtained for HMX and HMX/TNT composites depending on the experimental conditions (temperature, pressure, solution concentration…) used during the elaboration. For this purpose, the results obtained from scanning electron microscopy, X‐ray diffraction and Raman spectroscopy are discussed.     

超细HMX的表面能研究

用DCAT21型表面/界面张力仪测量了原料HMX（奥克托今,45μm～62μm）、超细HMX（0.2μm～1.7μm）和黏结剂FPM2602的接触角,并计算出它们的表面能。分析了HMX随粒径变化时其表面能的变化规律和黏结剂包覆超细HMX表面能的基本要求。结果表明,细化HMX表面能随粒径的减小有增加的趋势;黏结剂的表面能低于超细HMX的表面能,理论和实验均证明黏结剂FPM2602能包覆于超细HMX的表面。